Calculating machines



June 21, 1966 J. G. LLOYD 3,257,658

GALCULATING MACHINES Filed July 31. 1963 5 Sheets-Sheet 1 S Qkmk June 2l, 1966 J. G. LLoYD CALCULATING MACHINES Filed July 5l, 1963 5 Sheets-SheetI 2 /NVENTOR John George Lloyd June 2l, 1966 J. G. LLOYD 3,257,658

CALCULATING MACHINES Filed July 51, 1963 5 Sheets-Sheet 3 Il o Nb: mb: il Q wm mt ew e IH.

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ATTORA/E United States Patent O 3,257,658 CALCULATING MACHINES John George Lloyd, London, England, assigner to Bell Punch Company Limited, London, England, a British company Filed July 31, 1963, Ser. No. 299,057 Claims priority, application Great Britaimluly 31, 1962,

Claims. (Cl. 340-365) This invention relates to calculating machines of the kind which include a keyboard for controlling the entry of numbers into a register and it is an object of the invention to provide an improved keyboard which is of particular use in a calculating machine having a register consisting of electronic counting devices.

In known electrical and electronic calculating machines having keyboards the actuation of .a key normally causes electrical contacts to be closed. It may happen that during the actuation of a key the contacts are closed and opened a number of times for very short periods. The resulting short breaks in the continuity of the circuit have no effect in the case of electrical calculating ma chines having components with a comparatively slow response. However, in a calculating machine with electronic counting devices these devices may have a very short response time with the result that errors are caused if' a switch is opened even for only a few microseconds during the actuation of a key.

Accordingly, it has been proposed in the copending application No. 185,286, filed April 5, 1962, now U.S. Patent No. 3,163,730 which is assigned to the assignee hereof, to provide a special form of rotary electrical switch in which the effect of a lateral component of pressure on the key is considerably reduced. The present invention aims to solve the same problem by eliminating the use of electrical contacts altogether.

Accordingly, the invention -consists in a calculating machine including a keyboard for controlling the entry of numbers into -a register, wherein said keyboard inclu-des at least one bank of cold-cathode trigger tubes each associated with the entry of a predetermined digit and each arranged to be rendered conductive by the proximity ot an earthed object. i

A trigger tube may be rendered conductive by virtue of the proximity of the earthed object either to the tube itself, for example, to a conductive coating on the glass envelope of the tube, or to a plate or the like electrically connected to an electrode, for example, the trigger electrode, of the tube. y

The earthed object may be, for example, an operators finger, or it may be an object moved by the operator, for example, by the depression of a key.

It is possible to arrange the circuit in such a way that once a trigger tube has been rendered conductive it remains conductive until the potential on one of the electrodes of the tube is changed. This condition is equivalent to key-set operation. Alternatively, it is possible to arrange that a trigger tube which has been rendered conductive ceases to conduct when the earthed object is removed from the vicinity of the tube or of the plate 'which is connected to one of the electrodes of the tube.

This condition is equivalent to key-responsive operation.

When a trigger tube is conductive, the ionised gas in the tube forms an electrical path between the anode and the cathode. Thus striking of the trigger tube, i.e. renden ing the tube conductive, is equivalent to the closing of mechanical contacts. Deionisation of the trigger tube, i.e. rendering the tube nonconductive, is equivalent to the opening of the mechanical contacts.

In. one `arrangement according to the invention an alternating voitage is applied to each electrode of a gasfilled trigger tube, the magnitudes of these alternating matically at the end artists Patented June 21, 1966 voltages and their relative phases being such as not to cause the tube to become conductive. The trigger electrode of the tube, however, is electrically connected to a conductive coating on the underside of a transparent panel. When the operator places a finger on the panel, capacitive coupling is produced between the trigger electrode and earth. The magnitudes of the potentials applied to the tube are such that under these conditions the tube strikes, i.e. becomes conductive. lf key-respon sive operation is required, the potentials are such that, when the operators finger is removed from the panel deionisation occurs, i.e. the tube ceases to be conductive. It, however, key-set operation is required, the potentials are arranged to be such that, even when the operators finger is removed from the panel, the tube remains ionised, and thus continues to conduct. Deionisation may then be produced at the end of a calculation by modification of the potential on one of the electrodes of the tube.

In an alternative arrangement according to the invention a special gas-filled trigger tube is used having a conductive coating applied to the glass envelope of the tube. The arrangement of the electrodes in the tube and the potentials applied to the tube are such that, when an earthed object is placed in the proximity of the conductive coating on the tube, the tube is caused to strike. Deionisation may again be produced either merely as a result of the removal of the earthed object or by the reduction of the potential between the anode and cathode of the trigger tube to a value below the maintaining voltage. A special circuit may be provided to cause this reduction and this circuit may be operative autoof a calculation, or it may be caused to operate as a result of the actuation of a special key by the operator.

In so'me calculating machines the normal key-operated switches are required to pass pulses with fast rise and tall times and the ionised path of a trigger tube may not be satisfactory for this purpose, since it may cause unacceptable distortion of the pulses. In this case striking of the trigger tube may be used to control a gate through which pulses may be passed without undue distortion.

A further method of operating a calculating machine in accordance with the invention is to arrange the trigger tubes in a ring or rings. In the case of a ten-key machine only onering is necessary, but in the case of a machine having a plurality of banks of keys the trigger tubes associated with each bank will be arranged in a ring. This ring can be equivalent to any well-known gas trigger tube ring counter .having an input terminal and arranged so that when input pulses are applied to the input terminal the glow is stepped forward from the conductive trigger tube to the next trigger tube in succession in the ring. In a decimal machine there will be ten trigger tubes in the ring, or in each ring, and the arrangements for causing one particular tube in the ring to become conductive may be equivalent to those described above. However, after one tube in the ring has been fired, pulses are applied to the input terminal to cause the glow to step round the ring. The arrangement may be such, for example, that a carry pulse is taken from the trigger tube which represents Zero and the glow is stepped until a carry pulse is received. If a group of ten pulses is used to step the counter, pulses are applied to the input of the ring until a carry pulse is received. The remainderv of the group of ten pulses will then be applied to the register vand it will be seen that this number will be equal to the In an arrangement of the kind just described above the trigger tube which is fired by the operator is not used as a switch lbut as a temporary information store from which the information is extracted either immediately or if desired after asuitable delay.

Methods of performing the invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 illustrates parts of4 a calculating machine having a keyboard in accordance with the present invennon;

FIGURE 2 illustrates a modification of a part of the' circuit arrangement illustrated in FIGURE l, and

FIGURE 3 illustrates a further embodiment of the invention.

In FIGURE 1 of the drawings there are illustrated parts of a calculating machine generally similar to that described in my British Patent No. 925,161 but having a keyboard in Aaccordance with the present invention. The calculating machine includes a plurality of orders of keys and a plurality of counting devices arranged to form a register, but only one order of keys 1K .and only one register 1R are shown in the drawing.

The order of keys 1K includes a plate of transparent insulating material behind which are arranged a plurality of metal discs K1 to K9. Each of these discs is provided with a cut-out portion in the shape of the number represented by the respective key. Thus the disc K1 is provided with a cut-out portion in the shape of the numeral 1, the disc K2 with a cut-out portion in the form of the numeral 2, and so on up to the disc K9 which has a cut-out portion in the shape of the numeral 9. Behind each disc is one of a series of gas-iilled glow lamps N1 to N9. Behind the disc K1 is the glow lamp N1, behind the disc K2 is the glow lamp N2, and so on up to the glow lamp N9 which is located behind the disc K9.

Each of the discs K1 to K9 is connected to the trigger electrode of one of a series of gas-filled trigger tubes V1 to V9. The anode of each of the trigger tubes V1 to V9 is connected through a respective one of a series of inv vice T. The output of the AND gate 1GA is connected dividual resistors R1 to R9 to a line G which is connected through a common resistor R10 to the positive terminal 11 of a source of direct current. The cathode of each 'of the trigger tubes V1 to V9 is connected through a respective one of a series of individual resistors R11 to R19 to a line F which is connected through a common resistor R20 to the negative terminal 12 of the source of direct current.

Each of the glow tubes N1 to N9 is connected across a respective one of the resistors R1 to R9. Thus the tube N1 is connected across the anode resistor of the tube- V1, the glow tube N2 is connected across the anode resistor of the trigger tube V2, and so on up to the glow tube N9 which is connected across the anode resistor of the trigger tube V9.

The calculating machine includes a common pulse generator PG which produces ten pulses during each cycle of operation. This pulse generator has an output terminal P0 on which a single pulse appears at the beginning of each cycle. This pulse is applied through an amplifier TA to the input of a timing device T. The timing device has 16 output terminals T0 to T15 and each of these terminals can be rendered positive in succession when positive-going pulse appears on the output 1, two positivegoing pulses appear on the output 2, three positive-going pulses appear on the output 3 and so on up to the output 9 on which nine positive-going pulses appear.

The line G is connected thr-ough a capacitor C21 to one input of an AND g-ate 1GA, another input of which through an amplifier 1A to a pulse counter 1R which constitutes one order of the register of the calculating machine.

The negative terminal 12 of the direct current source which is connected between the cathodes and anodes of the trigger .tubes V1 to V9 is connected to one terminal of an alternating current source 13, the other terminal of which is connected to earth. The various potentials and `component values in the circuit are so arranged that -normally none of the trigger tubes V1 to V9 is conductive, with the result that none of the lamps N1 to N9 is lit. However, if the operator places a finger on one of the keys, the resulting capacitive coupling lbetween earth and the respective one of the discs K1 to K9 causes a suiiicient proportion of the potential of the alternating current source 13 to lbe applied to the trigger electrode of the associated trigger tube to cause that tu'be to tire.

Before the operator touches one of the keys, since no current is fiowing through the resistor R20, the line F lis maintained at a comparatively negative potential, with the result :that a negaitve potential is applied to the terminal T0 of the timing device T to prevent that device from being stepped by the P0 pulses yfrom the pulse generator. Under these conditions, none of the output terminals T1 to T15.of the timing device T can `be energised and accordingly neither the AND gate 1GA associated with the counting device 1R nor any of the other GA gates associated with the remaining counting devices in the register (each of which is controlled 'by a respective one of the terminals T2 to T14) can be opened. Further, until the operator touches one of the keys, the trigger tubes V1 to V9 are non-conductive and hence no pulses from the pulse generator PG can pass through any of these tubes to the line G. On the other hand, when the operatorl ,becomes conductive the potential of the line F will be made more positive and the inhibition will be removed from the timing device T. Accordingly when the next P0 pulseis applied to the timing device it will step so that the terminal T1 is made positive and the AND gate 1GA is opened.

It will be assumed for the purpose of this description that the calculating machine is arranged for key-responsive -operation and the sequence of events will be described, by way of example, following the placing of the operatorsinger on the insulated plate above the disc K3. As previously explained, capacitive coupling between the operators iinger and the disc K3 will cause the tu'be V3 to tire with the result .that current will flow through the resistor R3 and the glow tube N3 will lbe illuminated behind the cut-out portion of the disc K3. This cut-out portion will normally bearranged to ibe suiiiciently large for the glow :to be visible even when the operators iinger is still over the disc.

When the tube V3 becomes conductive the potential of the line F will be made more positive and the inhibition will `be removed from the timing device T. As a result the next P0 pulse will cause the timing device T to step from 0 to l so that the output terminal T1 is made positive. Thus the gate 1GA is opened and three pulses will be applied from the output P3 of the pulse generator :through the conductive tube V3, the capacitor C21, the open AND gate 1GA and the amplifier 1A to the input of the counting device 1R, the content of which will accordingly be increased by three.

Assuming that the operators iinger remains .over the disc K3, the tube V3 will remain conductive but the next P0 pulse from the pulse generator will step the timing device T to T2 with the result that the gate 1GA will be closed. Successive P0 pulses will step the timing device T unztil it reaches T when an inhibiting potential will be applied to the pulse generator PG to stop it. The apparatus willremain in this-condition until the operators finger is removed from the vicinity of the disc K3. Since it has been assumed that :the machine is arranged for keyresponsive operation, the potentials and circuit values are assumed to 4be such that removal of the triggering potential on the trigger electrode of the tube V3 Iwill cause the tube ,V3 to return to its non-conductive state. Unless the deionisation time of the trigger tube is so long that if the operators finger were tto be removed immediately after the tube V3 had 'been fired the tube would still remain conductive long enough to pass the pulses from :the pulse generator, arrangements must be provided to delay the deionisation of the tube for this time.

When the tube V3 ceases to conduct the line F will again become neg-ative and the timing device T will be caused to step to Tt). Thus the inhibition will be removed from the pulse generator which will recommence to cycle. Accordingly if a further key is now touched a further nurnber will be inserted into the register, the cycle 'of events being ras described above.

If key-set operation is required, a further resistor may lbe connected in series with R10 and the potentials and values may be so `selected that with the further resistor lshorted conduction will be maintained in any of the trigger tubes V1 to V9 even after removal of the triggering potential, whereas removal of the short from the further -resistor will cause the anode potential on any conductive trigger :tube to drop lbelow the maintaining potential. The contacts of a relay may lbe connected across the further resistor and these contacts will normally be closed. However, the relay will be arranged to open these contacts at the conclusion of a calculation.

As has already been explained, it may happen in some cases that the ionised path of the conductive trigger tube may not be satisfactory for passing pulses having fast rise and fall times. In such cases, the embodiment of the invention illustrated in FIGURE 1 may be modiiied in the manner shown in FIGURE 2. According to this modification the conductive trigger tube is used to control a gate and the pulses from the pulse generator are passed through the gate instead of through the anodelcathode path of the tube itself. Only the components associated with one key are shown in FIGURE 2, .but it will be clear to anyone skilled in the art how the components associated with the remaining keys may be connected.

In the arrangement shown the anode of the trigger tube V1 is connected through the resistor R1 to the positive terminal 11 of the power supply and the cathode of the tube is connected through the resistor R11 to the anodes of two rectiliers W31 and W32. The cathodes of the two rectiers W31 and W32 are connected through resistors R31 and R32 to the negative terminal'12 of the power supply. As in the case of the embodiment illustrated in FIGURE l, the trigger electrode of the tube V1 is connected to the disc K1, the glow tube N1 is connected across theresistor R1 and the negative terminal 12 of the power supply is connected to earth through a vsource of alternating current 13.

The cathode of the rectier W31 is connected to the P1 terminal of the pulse generator PG and the cathode of the rectier W32 is connected to the line G, and thence to the capacitor C21. In this embodiment the power f supply is not connected through the resistor R10 to the line G.

If the operator touches the plate above the Vdisc K1 the tube V1 will tire and current will ow through both the rectiiiers W31 land W32. Since both the rectiiers are conductive the application of the positive pulse from the .pulse generator to the cathode of the rectifier W31 will cause the cathode of the rectifier W31 alsoto become more positive and thus the positive pulse will appear ony the line G. It is to be noted that a positive pulse will also appear on the line G when the trigger tube V1 becomes conductive, but this pulse will not pass through the AND gate IGA since this gate can never be open at this time as the timing device T cannot step to T1 until the inhibition has been removed from the terminal T0.

It is to be understood that the negative terminals of the power supplies for all the components of the circuit arrangements illustrated in FIGURES 1 and 2 must be connected to the terminal 12 and not to earth, since, otherwise, the alternat-ing potential of the source 13 may upset the operation of these components.

In the embodiment of the invention illustrated in FIG- URE 3, the trigger tubes associated wtih each bank of keys are arranged in the form of a ring counter. The arrangement illustrated includes nine keys, each of which consists of a metal disc mounted on the back of a plate of insulating material having the numerals 1 to 9 engraved above the discs. The discs are indicated by the reference numerals K1 to K9, the numeral l1 being engraved above the disc K1, the reference numeral 2 being engraved above t-he disc K2, and so on. Associated with the discs K1 to K9 are nine gas-filled double trigger tubes T1 to T9 each of which has two trigger electrodes. The disc K1 is connected to the first trigger electrode of the trigger tube T1, the disc K2 is connected to the lirst trigger electrode of the trigger tube T2, and so on up to the disc K9 which is connected to the lirst trigger electrode of the trigger tube T9. In addition to the double trigger tubes T1 to T9, a further trigger tube T0 having a single trigger electrode is included in the ring. The second trigger electrode of each of the trigger tubes' T1 to T9 is con nected through a respective one of capacitors C1 to C9 to an input l-ine L. Further, the trigger electrode of the trigger tube Tt) is connected to the line L through a capacitor C0. The anodes of all the trigger tubes T0 to T9 are connected through a common resistor R10 to the positive terminal 11 of a direct-current source andthe cathodes of all the trigger tubes T0 to T9 are connected through individual resistors R0. to R9 and a common resistor R11 to the negative terminal 12 of the directcurrent source referred to. Further, the cathode of each of the trigger tubes T1 to T9 is connected through an individual one of resistors R21 to R29 to the trigger electrode of the next succeeding trigger tube in the r-ing, the cathode of the trigger tube T9 being connected through the resistor R29 to the trigger electrode of the trigger tube T0. The first trigger electrodes of the triggertubes T1 to T9 as well as being connected to their associated discs are also connected through individual resistors R41 to R49 to a line A which is used to provide an initial priming 'bias on these tubes.

In addition to the key bank and the trigger tubes already described, this embodiment of the invention includes two rectifiers W10 and W11 and a resistor R13, and B2, and three AND gates. The first AND gate includes two rectiiiers W10 and W11 and a resistor R13, the second AND gate includes two rectiers W12 and W13 and a resistor R14, and the third AND gate includes three rectiiiers W14, W15, and W16, and a resistor R15. The arrangement of each AND gate is such that a positive output appears only if positive potentials are applied to all of its inputs. The two bistable `devices B1 and B2 may be of any known type and are merely indicated.` by way of example, by means of two gas-filled trigger tubes in each case. Thus, the bistable device B1 is indicated as including trigger tubes TV10 and T11 and the bistable device B2 is indicated as including trigger tubes T12 and T13` The pulse generator PG is provided with twelve output terminals which are indicated by the reference numerals tl to 11. During -a cycle of operation of the pulse generator, one positive-going pulse appears on each of the terminals P0 to P11 in sequence. Thus, a positive-going pulse appears on the terminal P0 at the beginning of each cycle,`and a positive-going pulse appears 'on the terminal P11 at the end of each cycle. The terminal Z is connected to all the terminals P1 to P10 and thus ten positive-going pulses appear on this terminal during each cycle of operation, these ten pulses being preceded by a P pulse and succeeded by a P11 pulse.

Each of the bistable devices is designed to be set by the application of a positive pulse from the pulse genverator PG to the trigger electrode of one of its two trigger tubes and to be unset by the application of a positive pulse from the* pulse vgenerator to the trigger electrode of its other trigger tube. A positive output potential may be obtained from the cathode of the one trigger tube when the device is set and from the cathode of the other trigger tube when the device is unset. The length of each of the pulses producedpby the pulse generator, and the arrangement of each bistable device, are such that the state of a bistable device is not changed over until the end of the pulse from the pulse generator applied to the trigger electrode of one of its trigger tubes.

The trigger electrode of the trigger tube T11 is connected to the cathode of the trigger tube T0 and the trigger electrode of the trigger tube T is connected through a capacitor C10 to the output P0 of the pulse generator PG. The cathode of the trigger tube T11 is connected to the cathode of the rectifier W14 which constitutes one of the inputs of the third AND gate and the cathode of the trigger tube T10 is connected to the cathode of the rectifier W10 which constitutes one of the inputsl of the first AND gate. The trigger electrode of the trigger tube T12 is connected to the output P11 of the pulse generator and the trigger electrode of the trigger tube T13 is connected through la cap-acitor C11 to the output of the first AND gate. The cathode of the trigger tube T13 is connected to the cathode of the rectifier W16 which constitutes a second input of the third AND gate, and the cathode of the trigger tube T12 is connected to the cathode of the rectifier W13 which constitutes one input of the second AND gate. The second input of the first AND gate is constituted by the terminal Z as also is the third input of the third AND gate, while the second input of the second AND gate is constituted by the cathode of the tube T0. The junction of the anodes of the rectifiers W10 and W11, which junction constitutes the output of the first AND gate, is connected through a resistor R50 to la source of positive potential and through a rectifier W2 to the line L. The junction of the anodes of the rectifiers W12 and W13 and one end of the resistor R14, which junction constitutes the output of the second AND gate, is connec-ted through a rectifier W1 to the line A. The junction of the anodes of the rectifier-s W14, W and W16 with the resistor R15, which junction constitutes the output of the third AND gate, is connected to the input PC of a pulse counter or register.

The cathode of the trigger tube T13 is connected through a rectifier W3 and a resistor R51 to oneterminal of Ia capacitor C12 the other terminal of which is connected to the negative terminal 12 of the direct-current power supply. The junction of the resistor R51 and the capacitor C12 is connected through a rectifier W4 to the trigger electrode of the tube T11. The arrangement is such that, when the bistable device B2 is set (with the trigger tube T13 conducting), the capacitor C11 charges through the rectifier W3 and the resistor R51, but the rectifier W4 is so directed that current cannot flow through it from the cathode of the tube T0 to charge the capacitor when the tube T0 is conductive. The value of the capacitor C12 is such that when it has been charged it delays the setting of the bistable device B1 for about one second.

The negative terminal 12 of the direct-current source, which is connected between the cathodes 'and anodes of the trigger tubes T0 to T9, is connected to one terminal of an alternating current source 13, the other terminal of which is connected to earth, and the various potentials and component values in the circuit are so arranged that ythe trigger tube T0 is conductive when the apparatus is first switched on. Under these conditions, a small positive bias is 'applied from the line A to the first trigger electrode of each of the trigger tubes T1 to T9, since both inputs of the second AND gate are energised (i.e. rendered positive), the one input being energised because the bistable device B2 is in the unset state (i.e. tube T12 is conductive) and the other input being energised because the tube T0 is conductive. The initial priming bias on the line A is so related to the other potentials in the circuit that, if the operator places `a finger on one of the keys, the resulting capacitive coupling causes a sufiicient proportion of the potential of the alternating current source 13 to be applied to the first trigger electrode of the associated trigger tube to cause that tube to fire.

Before the operator touches one of the keys, the bi stable device B1 is in the unset state With the tube 11 conducting and the bistable device B2 is in the unset state with the tube T12 conducting. Under these conditions, a positive potential is applied from the cathode of the tube T11 to the cathode of the rectifier W14 which constitutes the first input of the third AND gate, but this AND gate is maintained closed by the negative potential applied from the cathode of the tube T13 in the bistable device B2 to its second input which is constituted by the cathode of the rectifier W16. A -negative potential is applied by the cathode of the non-conductive tube T10 in the bistable device B1 to the cathode of the rectifier W10 so that the first AND gate is also maintained closed. A P11 pulse is applied to `the trigger electrode of the tube T12 at the end of each cycle of operation of the pulse generator, but these pulses have no effect since the tube T12 is 'already conducting, so that the second AND gate remains open. Further, it is to be noted that, although P0 pulses are applied to the trigger electrode of the tube T10 through the capacitor C10, these pulses have no effect since the bistable device B1 is maintained in the unset state by the positive potential applied to the trigger electrode of the tube T11. It a P0 pulse does cause the tube T10 to become conductive momentarily, the resulting positive pulse on its cathode cannot pass through the first AND gate since no pulse appears on the terminal Z at the time ofthe P0 pulse.

For the purpose of the following description of the operation of the embodiment of the invention illustrated in FIGURE 3, it will be assumed that the operator has placed a finger on the key 3 with the result that the trigger tube T3 will have fired. When the trigger tube T3 fires, the additional voltage drop in the resistor R10 reduces the anode-cathode potential in the tube T0 below the main- 'taining potential with the result that the tube T0 ceases to conduct. Whenthe tube T0 ceases to conduct, its cathode becomes less positive with the result that the second AlN gate is closed and the priming bias is removed from the line A so that the position of the operators finger ceases to have any further efTect whether it is left 1in the key 3, removed altogether, orA placed on another After the operator has touched the key 3 so that the tube T0 has ceased to conduct, the positive potential is removed from the trigger electrode of the tube T11 in the bistable device B1 and the neXt P0 pulse which is applied through the capacitor C10 to the trigger electrode of the tube T10 will set state in which the tube T10 conducts in place of the tube T11. As a result, a positive potential will be applied to the cathode of the rectifier W10 from the cathode of the tube T10` and the first AND gate will be opened. Accordingly, the pulse P1 following the P0 pulse which set the bi-stable device B1 will be applied through the first AlND gate to the line L and thence through the capacitors C1 to C9 to the second trigger electrodes of change this bi-stable device to the all the tubes T1 to T9. The magnitude of this pulse is such that it will have no effect on any of the trigger tubes except tube T4 which is primed by the bias applied to its sec-ond trigger electrode through the resistor R23 from the cathode of the conductive tube T3. Thus the tube T4 will conduct in place of the tube T3. Similarly the P2 pulse will cause the tube TS to conduct in place of the tube T4 and so on until the P7 pulse causes the tube T to conduct in place of the tube T9.

In .addition to being coupled to the trigger electrodes of the tubes Tt) t-o T9 through the capacitors C0 to,C9, the line L is also coupled through the capacitor C11 to the trigger electrode of the tube T13. Thus, the P1 pulse is applied to the tube T13 and sets the bi-stable device B2 with the tube T13 conducting in place of the tube T12. Thus, while the. ring counter is being stepped by the pulses from the pulse generator PG, a positive potential is applied to the cathode of the rectifier W16 in the third AND gate, but a negative potential is applied to the cathode of the rectifier W14 since the tube T11 in the first bri-stable device B1 is non-conductive. Thus the third AND gate is -maintained closed and the pulses from the terminal Z of the pulse generator PG are not applied to the input terminal PC of the pulse counter or register. However, when the glow is stepped round the ring to the tube T0, the bi-stable device B1 is changed back to the unset state with the tube T11 conducting. Thus the third AND gate is opened and the rst AND gate is closed. It is to be noted that the setting of the bistable device B2 removes the positive potentialfrom the cathode of the rectifier W13, so that the second AND gate remains closed even when-the tube T0 again becomes conductive. F[ihus there is no priming bias on the line A and the glow remains on the tube T0, even if the operators finger is `still on one ot the keys. The pulses P8, P9 and P10 from the pulse generator are applied through the third AND gate to the terminal PC and thus cause the count in the register to be increased by three. The P11 pulse is not applied to the terminal Z, but is applied to the trigger electrode of the tube T12 and thus changes the bi-stable device B2 back to the unset state. As a result the second AND gate is opened and the third AND gate is closed. The following P0 pulse is applied through the capacitor C10 to the trigger electrode of the tube T10 in the bi-stable device B1, but is unable to set this bi-stable device because the positive potential is maintained on the trigger electrode of the tube T11. If the operators linger is still on the key the tube T3 will again become conductive and the tube T0 will become non-conductive. However, the positive potential will still be maintained for a further second on the trigger electrode of the tu-be T11 because of the charge on the capacitor C12. When this capacitor has discharged through the rectier W14 and the resistor R0, the next P0 pulse will set the bi-stable device B1 and a further three will be added into the register. This form of operation is similar to that provided on certain known electrically operated calculating machines in which the maintenance of pressure on a particular key causes repeated addition of the digit represented by that key into the register. If only a single addition is required, the operators iinger must be removed from the key within one sec-ond.

It is to be understood that the power supplies for all parts of the arrangement described must be connected to the terminal 12 and n-ot to earth in order to prevent the appearance of the alternating potential of the source 13 across parts of the circuit where it might upset the operation.

It will be appreciated that many modiiications may be made in the circuit arrangements described without departing from the scope of the appended claims. In particular, instead of using a trigger tube having a trigger electrode connected to an external plate it is possible to use a tube having a conductive coating which may be used directly for causing triggering of the tube when it is touched by an operators nger. Such a tube is illus-i trated', for example, in FIGURE 25 of British patent specification No. 732,018. In this case, it is advantageous to use a high frequency oscillator as the alternating current source 13 and it is to be understood that such an alternating current source may be used in any of the other embodiments described,

In a further modification of the invention, a pivotable or reciprocable key stem is provided above each of the discs K1 to K9 and an ea-rthed plate is arranged on the key stem so that when the key is actuated the earthed plate is brought near enough to the associated disc to cause triggering of the respective trigger tube. 1f desired, in such an arrangement mechanical latching ot the keys may be provided instead of the electronic latching described, and in addition mechanical operation of the start contact may be provided instead of the arrangements described.

Finally, it is to be unde-rstood that the invention may be applied to many different types of calculating machine, but it is primarily designed for, and has been described With reference to a calculating machine of the type described in British Patent Specication No. 925,161. The pulse generator PG, the timing device T and the counting device R, all yused in the embodiments of the present invention, may all be of the kind described in that patent specirication. i

What I claim as my invention and desire `to secure by Letters Patent of the United States is:

1. In a calculating machine, digit-entry controlling apparatus comprising an electrically-operated counting device, a pulse generator, a plurality of gas-filled trigger tubes each controlling the entry of a predetermined number of pulses from said pulse generator into said counting device, and means for causing any one of said trigger tubes to be rendered conductive by the proximity of an earthed object.

2. In a calculating machine, digit-entry controlling apparatus comprising an electrically-operated counting device, a multi-output pulse generator arranged to produce a different number of pulses at each of its outputs during each cycle of operation, `a plurality of gas-lled trigger -tubes each connected between a respective output of the pulse generator and the counting device, a plate of insulating material, a plurality of metal discs secured to said plate and each connected to the trigger electrode of one of said trigger tubes, a source of direct-current supply for said trigger tubes, and a source of alternating current connected between earth and the negative terminal of said direct-current source.

3. A calculating machine comprising an electricallyoperated counting device, a multi-output pulse generator having a plurality .ofoutput terminals at which diierent numbers of pulses appear during each cycle of operation of the generator, a plurality of gate circuits each connected between one of said output terminalsand ythe input of said counting device, a plurality of gas-filled trigger tubes each controlling one of said gate circuits, and means for causing any selected one of said trigger tubes to be rendered conductive by the proximity of an earthed object.

4. A calculating machine comprising an electricallyoperated counting device, a multi-output pulse generator having a plurality of output terminals lat which diierent numbers of pulses appear during each cycle of operation of the generator, a plurality of gate circuits each connected between one of said output terminals and the input of said counting device, la plurality of gas-tilled trigger tubes each controlling one of said gate circuits, a plate of insulating material displaying a plurality `of numerals, and means for rendering conductive that one of said trigger tubes which controls the gate circuit connected to the generator output terminal at which is produced a number of pulses equal to any numeral displayedon said plate when the plate is `touched in the vicinity of that numeral.

5. A calculating machine comprising an electricallyoperated counting device, a multi-output pulse generator having a plurality of output terminal-s at which diierent numbers of pulses appear during each cycle of operation of the generator, a plurality of vgate circuits each Connected between one of said output terminals V'and the input of said counting device, a plurality of gas-filled trigger tubes each controlling one of said gate circuits, a plate of insulating material, a plurality ofV metal discs located behind said plate :and each having a cut-out portion representing a numeral, means connecting each, of said discs to the trigger electrode of a respective one of said trigger tubes, a plurality of glow tubes each located behind a respective one of -said discs and connected in circuit with the associated tube.

References Cited by the Examiner UNITED STATES PATENTS 11/1953 Quinby 23S-145 2,659,533 2,914,667 1'1/1959 Branch u 328-97 3,052,849 9/1962 McCurdy 328-97 l0 NEIL C. READ, Primary Examiner.

T. B. HABECKER, Examiner. 

1. IN A CALCULATING MACHINE, DIGIT-ENTRY CONTROLLING APPARATUS COMPRISING AN ELECTRICALLY-OPERATED COUNTING DEVICE, A PULSE GENERATOR, A PLURALITY OF GAS-FILLED TRIGGER TUBES EACH CONTROLLING THE ENTRY OF A PREDETERMINED NUMBER OF PULSES FROM SAID PULSE GENERATOR INTO SAID COUNTING DEVICE, AND MEANS FOR CAUSING ANY ONE OF SAID TRIGGER TUBES TO BE RENDERED CONDUCTIVE BY THE PROXIMITY OF AN EARTHED OBJECT. 